A Long-term Safety Study With Tapentadol ER and Oxycodone CR in Patients With Moderate to Severe Pain Due to Chronic, Painful Diabetic Peripheral Neuropathy (DPN)

Inclusion Criteria:

• Man or woman aged 18 years or older

• Patients with Type 1 or 2 diabetes mellitus must have a documented clinical diagnosisof painful diabetic peripheral neuropathy with symptoms and signs for at least 6months, and pain present at the time of screening

• Diagnosis must include pain plus reduction or absence of pin sensibility and/orvibration sensibility on Total Neuropathy Score - Nurse (TNSn) examination in lowerand/or upper extremities at screening

• The investigator considers the patient's blood glucose to be controlled by diet, orhypoglycemics, or insulin for at least 3 months prior to enrolling in the study (thiscontrol should be documented by figures of glycated hemoglobin (HbA1c) no greater than 11% at screening)

• Patients have been taking analgesic medications for the condition for at least 3months prior to screening (patients taking opioid analgesics must be dissatisfied withcurrent treatment, and patients taking non-opioid analgesics must be dissatisfied withcurrent analgesia)

• Patients currently requiring opioid treatment must be taking daily doses of anopioid-based analgesic equivalent to <=160mg of oral morphine

• Patients with baseline score for average pain intensity in the previous 24 hours of =>4 on the 11-point numerical rating scale (NRS) at the beginning of the titrationperiod

Exclusion Criteria:

• Significant pulmonary, gastrointestinal, endocrine, metabolic (except diabetesmellitus), neurological, psychiatric disorders (resulting in disorientation, memoryimpairment or inability to report accurately as in schizophrenia, Alzheimer's disease)

• History of moderate to severe hepatic impairment

• Severely impaired renal function

• Clinically significant laboratory abnormalities

• Clinically significant cardiac disease

• History of seizure disorder or epilepsy

• History of any other clinically significant disease that in the investigator's opinionmay affect efficacy or safety assessments or may compromise patient safety duringstudy participation.